A general objective of the invention is to allow a correct demodulation of the signals received by a receiver even when the latter are disturbed by an interfering signal with constant envelope, that is to say with constant amplitude. More specifically, an objective of the invention is to enhance the efficiency, that is to say the signal-to-noise ratio, after demodulation, when the received signal superimposed on an interfering signal with constant envelope.
One possible solution for demodulating a signal disturbed by an interfering signal with constant envelope is described in the European patent application EP 2336800. This solution is based on a quantization of the signal on three levels: +1, 0 and −1. It entails quantizing the analogue signal specifically on the extrema and the 0 crossings of the signal to maximize the sensitivity relative to the useful signal without increasing the power of the noise. This solution presents the drawback of requiring a very precise locking of the automatic gain control in order to accurately position the amplitude of the received analogue signal relative to the quantization thresholds of the analogue-digital converter. Moreover, this solution offers sub-optimal efficiency.
Other receivers use a technique consisting in removing, from baseband complex digitized received signal, a component whose modulus is equal to the estimated mean modulus of the received signal and direction is equal to that of the received signal. This technique presents the drawback of requiring an architecture comprising algorithms of CORDIC (coordinate rotation digital computer) type in cascaded arrangement, which are complex to implement.